Do Trees Fill Out After Being Exposed to More Sunlight?

We had just cleared the lot for our new home and the trees they had selected to keep in our future back yard had a similar appearance: tall with few leaves until the top, where they were full. My question was were these trees going to fill out since they were now exposed to more sunlight because the surrounding trees had been removed.

The first year they did not. We had a nice canopy on top but the trees were pretty sparse below. This was unfortunate mainly because one of the trees is a sweet gum tree with brilliant red leaves in the fall and I wanted to enjoy them looking out our windows.

The second year, however, branches started sprouting all up and down the tree, meeting all the new sunlight. It’s likely that this happens even when there’s no light, but the branches die off if they’re not productive. It’s an amazing process. I also noticed that older branches about midway started dying. It’s not clear if this was because the tree was shifting resources to the new branches or because we had inadvertently killed the roots that fed those middle branches.

By the third year, more branches were starting and the ones from the previous year were getting bigger.

It’s clear from my trees (sweet gum, several types of oak), that trees do indeed fill out after they’re exposed to more sunlight. It reminds me of the neuroscience concept of brain plasticity and makes sense. Life adapts—even long-lasting plant life.